Resistance Strain Gauges Research Articles

A Special Robot for Precise Grading and Metering of Mushrooms Based on Yolov5

In order to accomplish accurate mushroom classification and measurement, it is necessary to optimize the existing classification algorithm and measurement devices, as well as to design a specific robot to improve classification accuracy and measurement efficiency. In order to achieve the above objectives, a research-level verification of mushroom grading using Yolov5 + OpenCV and a mushroom measuring system using a resistance strain gauge sensor was carried out. In the aspect of mushroom grading, a method based on the OpenCV visual library was used to identify the minimum quadrilateral outside the mushroom contour, allowing the size of the mushroom to be measured. The experiment’s results show that the method can assess target objects that are occluded with each other under different illumination conditions with 96% accuracy. In the measurement of mushrooms, the strain of the resistance is converted into an analog signal, and the weight of different grades of mushrooms is converted according to the linear relationship after processing by the detection circuit module. Through this method, the error range is successfully controlled within ±0.02 kg, which meets the requirements of accurate measurement of mushrooms. The results of field experiments show that the proposed accurate grading and measurement method of Lentinula edodes is effective and feasible, and provides technical support for the intelligent grading and measurement of Lentinula edodes in production units.

Experimental study on the vibration characteristics of fluid–structure coupling in the transition process of flexible bending pipes

The flexible bending pipes with large aspect ratios are more likely to cause large vibrations in the extraction of offshore oil and gas resources, which can accelerate the fatigue damage of the pipes. In order to explore the characteristics of fluid–structure coupling vibration during the transition period after the flexible bending pipe starts to transport fluid, an experimental platform of flexible bending pipes fluid–structure coupling vibration was created. The strain and vibration displacements of the pipe were measured by a resistance strain gauge and a high-speed camera system, respectively. According to the measure results, the largest values of stress and strain both were discovered at the pipe's two ends, and the maximum values of vibration displacement and vibration velocity were found in the middle of the pipe. The phenomenon indicates that the two ends of the pipe are more prone to fatigue damage. Moreover, the dynamic response and dynamic characteristics of the pipeline during the transition process were investigated. In addition, the effects of fluid flow rate, pipe wall thickness and different pipes on the dynamic response and dynamic characteristics of the pipe were also investigated in the present work.

Carbon Nanotube-Polyaniline Reinforced Flexible and Stretchable Strain Sensor with Enhanced Sensitivity for Smart Wearable and Skin-Mounted Applications

Flexible and stretchable strain sensors have emerged as promising components for integration into smart wearable devices and skin-mounted applications. These sensors enable accurate detection of physiological signals, thereby finding unique applications in diverse fields such as human health monitoring, soft robotics, human-machine interface, prosthetics, virtual reality, and professional sports. Two commonly utilized types of strain sensors are capacitive and resistive strain gauges, owing to their low production cost, simplified circuitry, and ease of construction. While resistive strain gauges exhibit high sensitivity, they are prone to nonlinearity and hysteresis. On the other hand, capacitive strain gauges demonstrate linear behavior with minimal hysteresis but offer lower sensitivity. In this study, we capitalize on the exceptional properties of carbon nanotubes, including high mechanical strength, electrical conductivity, and thermal stability, along with using polyaniline as an exemplary conductive polymer. These materials are employed as a reinforcing phase within the polymer matrix, while the dielectric layer is comprised of Ecoflex® 00-30. An interdigitated pattern is specifically designed for this strain gauge to enhance sensitivity. Through this research, we aim to develop a flexible and stretchable strain sensor with enhanced sensitivity and improved performance characteristics.

Dynamic Strain Measurement of Rotor Blades in Helicopter Flight Using Fiber Bragg Grating Sensor.

Fiber Bragg grating (FBG) sensor has a lot of advantages over the resistance strain gauge and has been used in many applications. However, there are few applications of rotor blade dynamic measurement in helicopter flight. In this paper, a method for blade dynamic strain measurement using an FBG sensor in a helicopter's real flight is presented. The corresponding measurement system is established and can eliminate the effects of the helicopter's electromagnetic environment on the electrical sensing components in the measurement system with the orthogonal frequency-division multiplexing modulation. The measured dynamic strains on the rotor blades of the helicopter in real flight contain six harmonic frequencies with the vibration characteristics of rotor blades, indicating that the established FBG measurement method and system have practical engineering applications.

Research on interactive force acquisition and active–passive mode determination of rehabilitation robot

Lower limb muscle strength is an important indicator of the effectiveness of rehabilitation training for patients with stroke and hemiplegia. When patients are trained with a lower limb rehabilitation robot, real-time human–machine interaction force acquisition can not only grasp the muscle strength of patients' lower limbs in time but also serve as an important reference for active/passive training mode. To accurately collect the human–machine interaction force to identify the patient's movement intention and determine the active/passive mode, a method is proposed to collect the human–machine interaction force based on a resistive strain gauge leg pressure sensor. The method can be applied to a variety of rehabilitation platforms to collect human–machine interaction force quickly and accurately and to identify and classify behaviors through probabilistic neural networks to determine patients' active/passive training patterns. By analyzing the active/passive walking of rehabilitation patients, the motor status of patients in that period is derived. The validity and correctness of the designed sensor and determination method were verified.

Structural Design and Static Calibration of Six-axis Force/Torque Sensor

A six-axis force/torque sensor is designed to solve the problems of the sensor with a resistance strain gauge. For instance, if the adhesive layer of the resistance strain gauge is not firm, the elastic sensing beam will have plastic deformation. The cylindrical conductive rubber is used as the sensing unit, which can detect force/torque by the change of the piezoresistive values. The units are arranged in a spatial eight-point staggered manner, which can reduce the dimensional coupling from the structure. The sensor static calibration is systematically analyzed and researched. The linear decoupling model of the measurement system that incorporating the Least Squares algorithm is established to reduce the dimensional coupling. The new type of sensor structure and static linear calibration algorithm proposed in this paper have good practical applications and popularization values.

Motor controlled system development with force-assistance using force/torque sensor for four-axis ceiling suspension system

Multi-axis force and torque sensors are type of transducers. They can measure force and torque in three dimensions. These sensors have multiple applications in robotic systems. The majority of these type of sensors use the strain measurement in any elastic structure. There are multiple approaches for strain measurement which include resistive strain gauge, piezo-electric and capacitive technologies. The evaluation of such a system can be done on various parameters, maximizing the acceptable sensing range while minimizing measurement errors/crosstalk is the main design challenge. In future, because force and torque sensors are necessary for service machines to interact with people in different situations, they will be widely deployed. However, it is challenging to find an appropriate force/torque sensor, and the cost is very high, because of certain design concerns and needs. This paper discusses an application based on the multi-axis force/torque sensor. A force-assisted control system has been proposed with simultaneous motorized action using force as feedback. The sensor needs and machine performance are reviewed after a thorough analysis of relevant data. This thorough investigation will benefit in the interfacing of specialized force/torque sensors to reduce crosstalk and aid in broadening the scope of service machines in which they can be used.

English

Devices that measure multi-dimensional force torque are suitable for various industrial equipment / machines / processes applications. Such sensors/sensing devices can read the direct physical force and convert it into digital data. In addition to resistive strain gauges, piezoelectric, capacitive, and optoelectronic methods, there are many other ways to measure the strain. Most of these rely on detecting stresses in an elastic structure as their underlying sensing principle. Forcetorque sensors will be necessary because future human assistive equipment/machines will be more interactive with human beings in various unstructured circumstances. Due to criteria and design considerations, not only finding a suitable forcetorque sensor is challenging, but also it incurs high costs. These sensors frequently produce data that include noise and crosstalk problems. A multi-axis force-torque sensor application is discussed in this paper. To decrease noise and crosstalk mistakes, the study presented a control system that simultaneously gives motorized action and uses force as feedback. The proposed system can be evaluated using a variety of metrics; however, the fundamental design challenge is to expand the allowed sensing range while minimizing measurement errors. After thoroughly investigating the necessary data, the requirements for sensors and machine performance are examined. The development of force-torque sensors in the machine and the expansion of their application in the various service machine industries will benefit from this in-depth examination.

Calibration Experiment and Temperature Compensation Method for the Thermal Output of Electrical Resistance Strain Gauges in Health Monitoring of Structures

Electrical resistance strain gauges are widely used in asymmetric structures for measurement and monitoring, but their thermal output in changing temperature environments has a significant impact on the measurement results. Since thermal output is related to the coefficient of thermal expansion of the strain gauge’s sensitive grating material and the measured object, the temperature self-compensation technique of strain gauges fails to eliminate the additional strain caused by temperature because it cannot match the coefficient of thermal expansion of various measured objects. To address this problem, in this study, the principle of the thermal output of electrical resistance strain gauges was analyzed, a calibration experiment for thermal output in the case of a mismatch between the coefficient of linear expansion of the measured object and the strain gauge grating material was conducted, and the mechanism for temperature influence on thermal output was revealed. A method was proposed to obtain the thermal output curves for different materials by using thermostats with dual temperatures to conduct temperature calibration experiments. A linear regression method was used to obtain a linear formula for the thermal output corresponding to each temperature. The thermal output conversion relationship was derived for materials with different coefficients of linear expansion. An in situ temperature compensation technique for electrical resistance strain gauges that separates the measured strain into thermal and mechanical strains was proposed. The results showed that the thermal output curve for the measured object can be calibrated in advance and then deducted from the measured strain, thus reducing the influence of temperature-induced additional strain on the mechanical strain. In addition, a new method was provided for the calculation of the thermal output among materials with similar coefficients of linear expansion, providing a reference for the health monitoring of asymmetric structures.

Dynamic large strain measurement under high-temperature environment using a modified FBG sensor and plasma surface treatment.

Large strain measurement under high-temperature environment has been a hot but difficult research issue in the fields of measurement and metrology. However, conventional resistive strain gauges are susceptible to electromagnetic interference at high temperature, and typical fiber sensors will be invalid under high-temperature environment or fall off under large strain conditions. In this paper, aiming to achieve effective and precision measurement of large strain under high-temperature environment, a systematic scheme combining a well-designed encapsulation of a fiber Bragg grating (FBG) sensor and a special surface treatment method using plasma is presented. The encapsulation protects the sensor from damage while achieving partial thermal isolation and avoiding shear stress and creep, resulting in higher accuracy. And the plasma surface treatment provides a new bonding solution which can greatly improve the bonding strength and coupling efficiency without damaging the surface structure of the object under test. Suitable adhesive and temperature compensation method are also carefully analyzed. Consequently, large strain measurement up to 1500 µɛ under high-temperature (1000°C) environment is experimentally achieved in a cost-effective way.

Experimental investigations of fractured rock deformation: A direct measurement method using strain gauges

Measuring fractured rock deformation under changing loading conditions is important in rock engineering projects to estimate rock strength and permeability. Measurement of deformations at less than micrometer level for rock fractures is difficult. To investigate the feasibility of the resistance strain gauge method, an experimental system was built to measure the fractured rock deformation due to cycling of confining pressure. The test results of different positions were compared and relatively reasonable test locations were selected based on the test data and regression analysis. The measurement tests were conducted on cylindrical samples with diameters of 50 mm and lengths of 100 mm of shale, granite, limestone, and marble containing a single fracture or two parallel fractures. The experimental results show that the strain gauge method and the proposed test point pattern perform well for measuring fractured rock deformation under changing loading conditions. The experimental data for the loading progress for a single fracture fits the existing fractured rock deformation models well (i.e., the Goodman model, Bandis model, and Sun model). For cyclic loading, observed cycles compared with the existing models and the hysteresis loop during deformation under cycling of the confining pressure, the strain-pressure curves of the loading and unloading processes are consistent with existing models. The strain gauge method provides a deformation measurement method of two parallel fractures. Under the pressure 15 MPa for plane α the deformation is in a state of opening with strain value more than 1003 με; but plane β is in a state of closure with strain value near −115 με.

Sensing Mechanisms of Flexible Pressure Sensors

In the first segment of this project, the merits of the flexible capacitive pressure sensor will be described. These benefits encompass lower power consumption, less signal drift, greater response repeatability, and others. However, as ductile materials are incompressible, the device's sensitivity won't be very good without adopting structures. The purpose and advantages of the resistance flexible pressure sensor will then be discussed, as well as its high nonlinearity and the metal-based strain effect of the resistance strain gauge, which results in mechanical deformation when an external force is applied and results in a corresponding change in resistance value. However, the output signal is weak because of the environment and time zone variations. The design and operation of the sensor will change. It is not appropriate for long-term monitoring due to its significant time and temperature drift and the potential that correct data may not be acquired after extended measurement. Additionally, it is sensitive to electromagnetic fields, vibration, radiation, air pressure, sound pressure, and air velocity. In the last part, the benefits of the flexible piezoelectric pressure sensor will be discussed, including its broad frequency range, high sensitivity, high signal-to-noise ratio, simple structure, dependable operation, and light weight. The disadvantage of piezoelectric sensors is that some of these materials have poor output direct current responsiveness and call for moisture protection, which calls for the usage of charge amplifiers or high input impedance circuits to address this shortcoming.

Monitoring and verification of micro‐strain generated inside the laminate subjected to thermal loading through fiber bragg grating sensors and classical laminate theory

AbstractFiber Bragg Grating (FBG) sensors possess enormous potential for the cure monitoring and integrity assessment of Carbon Fiber Reinforced Polymer (CFRP) composites. These sensors can be embedded inside the structure to monitor the strain in the desired region of interest. The strain on an FBG sensor can be calculated by measuring the change in the center wavelength of the sensor. This change in center wavelength is a function of temperature and mechanical strain. Therefore, temperature compensation is necessary for a precise mechanical strain measurement with an FBG sensor. In this study, FBG sensors are embedded in different layers of the CFRP laminate to record the mechanical strain caused by the thermal expansion, which happens under the influence of temperature. Classical laminate theory (CLT) is implemented to assess the accuracy of FBG sensor measurements and the strain data acquired from both FBG sensor and CLT correlates. Furthermore, a resistive strain gauge is deployed to measure the strain under the influence of temperature. It is depicted that strain values recorded by the strain gauge under the influence of the temperature do not agree with the strain measured by CLT, and an error of 150% occurs among their values.

Measurement of alternating and rotational magnetostrictions of Non-oriented silicon steel sheets

Extensive numerical analyses and experimental tests have shown that while major regions of magnetic cores in electromagnetic devices, such as transformers and rotating electric machines, are dominated by the alternating magnetic fields, the rotating magnetic fields exist in the corner joints of multi-phase transformers and the yoke area behind the teeth of rotating electric machines. These magnetic fields cause core losses due to hysteresis and eddy currents, mechanical vibration and acoustic noises due to magnetostriction. Many studies have been reported in the literature on alternating and rotational core losses and alternating magnetostriction, but not so much on rotational magnetostriction, especially in non-oriented (NO) silicon steel sheets. The vibration and noise caused by rotational magnetostriction are much higher than those caused by alternating magnetostriction. This paper reports the development of a magnetostriction measurement system consisting of a 2D symmetrical single sheet tester (SST) and resistance strain gauges. The selection considerations of resistance strain gauges are summarized. The alternating and rotational magnetostriction characteristics of a NO silicon steel, B35A300 (0.35 mm), are measured. Because the rotating magnetic field in the stator is not always ideally circular but more often elliptical, the magnetostriction under elliptical magnetizations with different axis ratios is also measured. The magnetostriction anisotropy of the NO steel sheet is observed and analyzed. The elongation and contraction under alternating, circular and elliptical rotating magnetizations with different axis ratios are discussed. The results can provide data support for calculating and designing multi-phase transformers and rotating electric machines under different types of magnetizations. The research can provide theoretical and practical guidance for mitigating mechanical vibration and acoustic noise caused by magnetostriction.

Analysis of Muscle Activity During Rowing Stroke Phases

Purpose Rowing engages large muscle groups, and EMG analysis is used to assess athletes' condition and refine sports technique. The aim of the experiment was to evaluate the muscle activation level during different phases of the rowing cycle on an ergometer. Methods In a study involving one professional and five amateurs, the mean EMG amplitudes from the quadriceps, gastrocnemius, biceps, and triceps brachii were analyzed during different phases of rowing. A comparison was made between the degree of muscle engagement during the exercise between the professional and inexperienced individuals, as well as among the different individuals during recordings obtained at different rowing speeds. The correlation coefficient between the values recorded using a strain gauge and the EMG amplitude recorded from the surface of the biceps and triceps brachii muscles was evaluated. Results The muscle activation pattern during rowing has a predictable character. A difference in the muscle activation pattern during rowing between the professional and amateurs was observed. The EMG signal is correlated with the force recorded by the resistive strain gauge only in the experienced rower at a pace of 20 and 25 cycles per minute. Conclusions Electromyographic analysis can be useful for assessing the correctness of rowing techniques. The activation pattern of muscles during rowing has a predictable nature. The force generated by the participants increases with an increase in rowing frequency.

Monitoring state of charge and volume expansion in lithium-ion batteries: an approach using surface mounted thin-film graphene sensors.

Accurate monitoring of battery cell state of charge (SoC) and state of health (SoH) is vital to the safe and effective operation of rechargeable battery systems such as those in electric vehicles yet remains a challenge while the system is in use. A new surface-mounted sensor enabling simple and rapid monitoring of lithium-ion battery cell SoC and SoH is demonstrated. Small changes in cell volume brought about by the expansion and contraction of electrode materials during charge and discharge are detected through monitoring the changes in electrical resistance of a graphene film in the sensor. The relationship between sensor resistance and cell SoC/voltage was extracted, enabling rapid SoC determination without interruption to cell operation. The sensor was also capable of detecting early indications of irreversible cell expansion due to common cell failure modes, enabling mitigating steps to be taken to avoid catastrophic cell failure.

Failure Analysis of Gantry Crane Slewing Bearing Based on Gear Position Accuracy Error

In large ports, shipyards, and other places of handling operations, gantry cranes are widely used. As a typical slewing crane, its slewing-bearing large gear ring is prone to tooth breakage problems due to the existence of long-term complex alternating load. This paper presents a new fault analysis method based on the gear position accuracy error. Firstly, the relative displacement relationship between the pinion and large gear ring and the large gear ring gear teeth stress nature were analyzed through the establishment of the rotary table structure, slewing bearing, and cylinder structure assembly finite element model. In addition, a dynamic data acquisition instrument and resistance strain gauge data were separately applied to analyze the pinion and large gear ring displacement along with cylinder structure stress for the test position accuracy error. The final results show that under the frontal load condition, the horizontal displacement deviation of the pinion gear and the large gear ring is approximately 2.9 mm, which leads to an increase of 23% in the stress value of the upper tooth root at the engagement of the large gear ring, causing extrusion and accelerating the fatigue and even fracture of the gear teeth.

Evaluation of thermal-drift effect on strain measurement of energy pile

Fiber Bragg grating (FBG) strain sensors and electrical resistance strain (ERS) gauges are typically utilized to monitor the internal deformation of structures. However, a common problem inherent in these sensors is the unwanted thermal drift in the measurement results. This study first investigated factors influencing the thermal strain measurements of FBG strain sensors and ERS gauges through a series of calibration experiments. The results demonstrate that the relative error caused by the thermal output of the heated connection cables was as high as 90 %. Then a correction method for the thermal drift of the strain measurement was proposed. This correction method reduced the relative difference between the strain readings of bonded ERS gauges and FBG sensors from 82.6 % to around 10–20 %. Finally, FBG strain sensors and ERS gauges were employed to monitor the strain of the energy piles under cooling and heating cycles. The difference between the corrected readings from FBG strain sensors and ERS gauges was less than ± 10 %. The experimental results also reveal that the monitoring reliability of the FBG strain sensors was higher than the ERS gauges.

A design of underwater soft gripper with water pressure sensing and enhanced stiffness

AbstractIn this paper, a hydraulic soft gripper for underwater applications is designed to provide a solution for improving the gripping force as well as the sensing capability of the soft gripper. The soft gripper is made of silicone and has an integrated semi-circular hydraulic network inside. To enhance the rigidity and grasping performance of the soft gripper, we have integrated a restriction layer consisting of a spring steel plate in the soft gripper. Meanwhile, to enhance the sensing capability of this soft gripper, we have designed a water pressure sensor based on resistance strain gauges and integrated it on the spring steel plate. Before fabrication, we determined the structural parameters of the soft gripper by geometric analysis. Then we experimentally evaluated its pressure-bearing capacity, bending performance, the role of spring steel plates, and the accuracy of the sensor.The experimental results show that the spring steel plate improves the gripping force of the soft gripper, the sensor also has high accuracy, and the built four-finger gripping system has good adaptability to objects of different shapes and weights.Compared with the existing solutions, this solution takes a simpler structural form while improving the gripping force and sensing ability of the soft gripper, and integrates the issues of improving the gripping force and sensing ability. The spring steel plate used in this paper not only improves the gripping force of the soft gripper but also provides a stable and reliable platform for installing sensors.

A Novel High-Sensitivity MEMS Pressure Sensor for Rock Mass Stress Sensing.

This paper proposes a novel high-sensitivity micro-electromechanical system (MEMS) piezoresistive pressure sensor that can be used for rock mass stress monitoring. The entire sensor consists of a cross, dual-cavity, and all-silicon bulk-type (CCSB) structure. Firstly, the theoretical analysis is carried out, and the relationship between the structural parameters of the sensor and the stress is analyzed by finite element simulation and curve-fitting prediction, and then the optimal structural parameters are also analyzed. The simulation results indicate that the sensor with the CCSB structure proposed in this article obtained a high sensitivity of 87.74 μV/V/MPA and a low nonlinearity error of 0.28% full-scale span (FSS) within the pressure range of 0–200 MPa. Compared with All-Si Bulk, grooved All-Si Bulk, Si-Glass Bulk, silicon diaphragm, resistance strain gauge, and Fiber Bragg grating structure pressure sensors, the designed sensor has a significant improvement in sensitivity and nonlinearity error. It can be used as a new sensor for rock disaster (such as collapse) monitoring and forecasting.